Double membrane pump



FIG. 1 is a front perspective view of a double membrane pump illustrating my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a left view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a front view thereof. 

CLAIM The ornamental design for a double membrane pump, as shown and described. 